This document provides a method for determining the chloride content in soap and soap products. The method involves precipitating fatty acids from an aqueous soap solution using calcium nitrate solution. The precipitate is washed to remove chlorides, which are then titrated with standard silver nitrate solution using potassium chromate indicator. The percentage of chlorides in the sample can be calculated based on the volume and normality of silver nitrate used and the mass of the original sample.

1. PREPARED BY: SABAH MUHYADEEN YOUSIF 1
Determination of chloride content in soap
and soaps product
Introduction:
This method determines the chlorides in the sample and is applicable to all soaps
and soap products, including those containing synthetic detergents. From an
aqueous solution of soap, the fatty acids are precipitated as insoluble calcium
soaps by the addition of calcium nitrate solution. This precipitate is washed free
of chlorides and the chlorides in the washings and filtrate estimated by titration
with standard silver nitrate solution, using potassium chromate as indicator.
Reagents:
1. Calcium Nitrate Solution — neutral, chloride-free and containing 20 percent
(m/v) of calcium nitrate crystals [ Ca (NO3)2, 4H2O ].
2. Methyl Orange Indicator — Dissolve 0.1 g in 100 ml of 95 percent rectified
spirit.
3. Dilute Nitric Acid — approximately 1 N.
4. Potassium Chromate Indicator — Dissolve 5 g of potassium chromate
(K2CrO4) in 100 ml of water.
5. Standard Silver Nitrate Solution — approximately 0 1 N.
Procedure
A. Weigh accurately about 10 g of the sample and dissolve in hot water in a 250-
ml tall form beaker, add 20 ml of the calcium nitrate solution, mix thoroughly,
cool and filter into a one-mark 250-ml volumetric flask. Wash the filter free from
chlorides using water allowing the washing to run into the flask. Shake the flask
and the contents and dilute to the mark.
B. Take 100 ml of the solution, neutralize to methyl orange indicator with dilute
nitric acid and titrate with silver nitrate solution, using potassium chromate
solution as indicator. Carry out a blank determination using the same quantity of
all reagents but except the sample.

2. PREPARED BY: SABAH MUHYADEEN YOUSIF 2
Calculation:
a) Chlorides (as NaCl), percent by mass =
b) Chlorides (as KC1), percent by mass =
where:
T = volume in ml of standard silver nitrate solution,
N = normality of standard silver nitrate solution, and
M = mass in g of the material taken for the test.
Reference: ISO 457:1976